She said her group, which works with marginalised women, had taken several calls from hijab-wearing women who reported being called “letter boxes”.

Johnson, who leaped back into contention to replace Theresa May as prime minister after resigning his post in protest against the government’s Brexit plan, made the controversial comments in a newspaper column on Monday.

Earlier in a newspaper column, Johnson said women who wear the niqab looked like “letter boxes” and “bank robbers”.

He has since faced a storm of protest from inside and outside the party. Both May and party chairman Brandon Lewis said he should apologise, as did civil society minister Tracey Crouch who called Johnson’s language “intentionally provocative”.